1. Field of the Invention
The present invention relates to the field of power electronics, and particularly to a switching regulator and a control circuit and a control method therefor.
2. Description of the Related Art
A switching regulator typically comprises a power stage and a control circuit. The control circuit can consider variations in an input voltage, internal parameters and external loads, and can regulate the ratio of on/off time of the switch system in the power stage, so that an output voltage or an output current of the switching regulator can be maintained as substantially constant. Therefore, the design of a particular control circuitry and approach is very important to the overall performance of the switching power supply. Thus, adopting different detection signals and/or control circuits may result in different control effects on performance.
Control circuits in the prior art implement control by means of voltage feedback and current feedback, which generate a switching control signal to control a power switch in a power stage in accordance with feedback signal from an output of the power stage and an expected reference voltage. In the prior art, a supplementary signal is superimposed to the feedback voltage or the reference voltage so that the control circuit can respond to variations in the power stage quickly.
However, control circuits using the supplementary signal would lose the control of the supplementary signal when the power stage switches to a large capacitance loaded or light loaded condition. Therefore, when the power stage switches back to a normal condition, there is required multiple cycles to recover a steady state. This results in that the voltage ripple may be at a high level.